Stash Tea: Tea Times - Milk Or Lemon For Your Tea?

Tea Times - Milk Or Lemon For Your Tea?

"Come, little cottage girl, you seem
To want my cup of tea;
And will you take a little cream?
Now tell the truth to me."

She had a rustic, woodland grin
Her cheek was soft as silk
And she replied, "Sir, please put in
A little drop of milk."

The benefits of adding milk or lemon juice to black tea brews are explained in scientific terms by Professor Michael Spiro of the Imperial College of Science, Technology and Medicine in London, England.

These verses, in the style of William Wordsworth, were written about a century ago by Barry Pain in his poem The Poets at Tea. And, indeed, milk has long been added by almost all tea drinkers in Britain, Ireland, and most Commonwealth countries and by many in the U.S. The earliest western observation of milk as an ingredient for tea was made by the Dutch traveler Jean Nieuhoff at a banquet given by the Chinese emperor in 1655 for 'barbarian' members of the Dutch embassy. The wife of the poet de la Sabliere introduced France to the custom of adding milk to tea in 1680, and it was around 1700 that milk or cream was first used by tea drinkers in the American colonies.

Milk-Tea Interaction

Black tea on its own has an astringent or puckering effect in the mouth. This arises from the polyphenols (catechins, theaflavins, thearubugins) or tannins which are the major constituents of black tea. They interact with ('attack') the proteins in saliva and on the surface tissue of the tongue and mouth. (A similar effect is produced by related tannins in young red wines which feel dry and rough in the mouth. Rare steak is a classic partner for such a wine, offering a decoy protein to these polyphenols and making the wine seem much smoother. A creamy sauce will also protect the palate in these circumstances.) The resulting feeling of astringency from the tea is greatly reduced by the presence of milk. Addition of milk therefore mellows the taste and also adds body to the liquor, although too much milk will detract from the characteristic 'bite' of the tea brew.

The role played by milk has long been ascribed to the casein in it. There are in fact four major types of casein which together account for some 80% of the protein in cow's milk. They form roughly spherical aggregates called sub-micelles, which in turn are held together by calcium phosphate in large casein micelles. What recent research has shown is that when milk and tea are mixed, the tea polyphenols are sequestered inside the casein sub-micelles. The tannin components are thereby protected from interaction with the proteins in the mouth and so the resulting beverage becomes much less astringent. Moreover, the fat component in the milk may act as a barrier cream, partially shielding our flesh from the remaining free polyphenols.

The type of milk used affects the organoleptic properties of the drink. Cream, or even milks which are too creamy, are apt to impart too fatty a taste. So are coffee whiteners which are made by emulsifying vegetable fat into glucose syrup. Skimmed milk, on the other hand, even though it contains as much casein as normal milk, produces a dull gray liquid without much body. Semi-skimmed milk is a good compromise and is now preferred by many tea drinkers.

When black tea is brewed in hard water containing calcium and bicarbonate ions, a thin dark film forms on the surface. This is composed of oxidized tea polyphenols together with a smaller amount of calcium carbonate (the limestone through which the water has passed). Such a film tends to stick to cups and mugs and is difficult to remove. A much more lightly colored film develops when milk has been added: Many of the tannin components are then confined inside casein micelles and much of the film is composed of milk fat. Milky tea films leave less unsightly marks in the crockery afterwards.

Milk in First or Tea First?

Media people interviewing scientists who have worked on tea almost invariably ask this question. To some extent, the answer depends on social factors such as the tradition of the household or hotel. However, the official view now is that it is best to put the milk into the cup first. This cools the first portion of the hot tea as it is poured in, reducing the risk of protein denaturation and scalding of the milk fat. It also has the advantage of automatically mixing the milk with the tea, eliminating the need to stir.

According to the student who worked in a vegan establishment, the question is even more relevant when soya milk is used. She told me that pouring tea onto the milk caused normal mixing, but when soya milk was added to hot tea it did not mix properly and produced floating feathery flakes.

Lemon Tea

Hot lemon tea is a popular and refreshing drink in Mediterranean and other hot countries where lemons are more readily available than fresh milk. The absence of milk also makes lemon tea a kosher drink for orthodox Jews at meals which include meat. Americans enjoy iced tea with lemon and other fruit flavors, as exemplified by the success of the recent Snapple products.

Lemon juice contains citric acid which largely prevents the ionization of the hydroxyl groups of the tea polyphenols. The spectrum of the more acidic lemon tea therefore differs from that of plain black tea, and the beverage color appears light yellow rather than the usual reddish brown. The fact that the hydroxy groups are almost un-ionized also restricts the interaction between the tannins and the proteins in the mouth -- and so significantly reduces the sensation of astringency. Moreover, lemon tea possesses a distinct advantage for tea drinkers in areas of hard water. The calcium and bicarbonate ions which this water contains are responsible for forming the unsightly dark tea films mentioned above. Both these ions are removed by the citric acid in lemon juice which complexes the calcium ions and converts the bicarbonate ions into carbon dioxide. The surface of lemon tea is therefore clean and no dark film deposits stick to the cup or glass afterwards.

Professor Michael Spiro is Emeritus Professor of Physical Chemistry and Senior Research Fellow in Chemistry at Imperial College of Science, Technology and Medicine in London.

Reprinted from Tea & Coffee Trade Journal, October 1996 with permission.

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